There exist keys that have one end secured to a yoke that is mounted between two cheeks of a casing to turn about a pivot axis between a position in which the key is retracted inside the casing and a position in which the key is extended. A control pushbutton is mounted in the yoke so as to be constrained to pivot therewith, and so as to slide between an extended position for blocking the yoke, in which position the pushbutton has studs received in notches of the casing that are positioned to correspond with each of the positions of the yoke, and a pushed-in position for releasing pivoting of the yoke, in which position the studs are disengaged from the notches. A spring is interposed between the casing and the control pushbutton to urge the yoke resiliently into its extended position and the control pushbutton into its blocking position.
The casing is generally made of a plastics material while the pushbutton is made of metal. It often happens that the casing includes opposite from the yoke an orifice for passing a keyring.